In oil and gas drilling process, various types of drilling fluids are used, mainly including water-based drilling fluid, oil-based drilling fluid, polymer drilling fluid and the like. Among them, oil-based drilling fluid further includes oil-in-water emulsified drilling fluid, whole-oil-based drilling fluid, reversibly emulsified oil-based drilling fluid and the like Whole-oil-based drilling fluid refers to an oil-based drilling fluid with oil-water ratio of 95:5 or above and mainly comprises oil, water and emulsifier. The whole-oil-based drilling fluid has the advantages of strong inhibitive ability, good lubricity, strong anti-pollution capacity and high thermal stability. However, as conventional whole-oil-based drilling fluid system has a high oil-water ratio and forms less emulsion, the suspending power of the system is poor. In general, a basic skeleton is formed through addition of organic clay to raise the suspending power of the system, whereas the addition of organic clay not only will lower the overall temperature resistance of the system (mainly because organic clay is not resistant to high temperature) but also affect oil and gas exploitation as organic clay will enter and damage the reservoir during well drilling.